Method of forming resist pattern, and exposure device

ABSTRACT

A method of forming a resist pattern and an exposure device using the method are provided in which a relatively large pattern, whose dimension is greater than a resolution limit of a KrF exposure technique, and an extremely fine pattern, whose dimension is less than or equal to the resolution limit of the KrF exposure technique, can be formed well and simultaneously. Two patterns are exposed simultaneously by deep UV light of a wavelength of 248 nm on a resist film  10  formed of TDUR-P015 and formed on a surface of an SiO 2  film  12.  The two patterns are: a circular pattern of a dimension which is made larger, in accordance with a shrinkage rate, than a finally required pattern dimension, which circular pattern is formed at regions to be shrunk; and a circular pattern of a dimension which is finally required, which circular pattern is formed at regions not to be shrunk. A UV light exposure amount, which is of an amount such that heat resistance of the TDUR-P015 forming the resist film  10  improves and the resist pattern does not shrink, is applied only onto the regions not to be shrunk of the resist pattern obtained by development. Then, high temperature bake processing at 135° C. for 60 seconds is carried out.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of forming a resistpattern and to an exposure device, and in particular, to a method offorming a resist pattern and an exposure device which are based on anexposure technique using a KrF excimer laser as a light source in theproduction of a semiconductor integrated circuit.

[0003] 2. Description of the Related Art

[0004] Conventionally, in manufacturing a semiconductor integratedcircuit, in order to form a more fine pattern, a KrF exposure techniquehas been mainly used, in which deep UV light having a wavelength of 248nm is emitted as exposure light from a KrF excimer laser light source.In this KrF exposure technique, it is possible to form a pattern ofabout 0.2 μm.

[0005] Japanese Patent Application Laid-Open (JP-A) No. 11-119443discloses, in such a KrF exposure technique, a technique in which a finepattern of about 0.2 μm or less is obtained by shrinking the resistpattern (e.g., shrinking the internal diameter of the hole patternformed at the resist) by baking the resist at a temperature which ishigher than the usual baking which is carried out in order to remove theresidual solvent and the residual moisture which remain after the resistpattern has been formed. In accordance with this technique, it ispossible to form a pattern of about 0.1 μm or less, which exceeds theresolution limit of the KrF exposure technique.

[0006] The method disclosed in the aforementioned JP-A-11-119443 issuited to the formation of an extremely fine pattern for which the size(dimension) of a feature (e.g., the diameter of a contact hole, thewidth of an embedded wiring, or the like) is less than or equal to theresolution limit of the KrF exposure technique. However, for arelatively large pattern whose feature dimension is greater than theresolution limit of the KrF exposure technique, the pattern after bakingdeteriorates, and thus, this method is not preferable.

[0007] For example, as illustrated in FIG. 10A, when holes (a contacthole pattern) of a diameter of about 0.25 μm and holes (a contact holepattern) of a diameter of about 0.5 μm are formed in a resist and theresist is baked for 60 seconds at around 135° C., as illustrated in FIG.10B, the side walls at the holes (the contact hole pattern) of adiameter of about 0.25 μm do not deform and only the diameter decreasessuch that holes of a diameter of about 0.1 μm are formed. However, atthe holes (the contact hole pattern) having a diameter of about 0.5 μm,the resist side walls forming the pattern curve towards the centers ofthe holes, such that deformed holes whose smallest diameter is 0.35 μmare formed.

[0008] When a resist having holes of such configurations is used as amask in the etching process which is carried out later, the portionscorresponding to the peaks of the convex shapes of the resist aregradually removed as the film to be processed, which is the layertherebeneath, is etched. In addition, the resist side walls are curvedtoward the centers of the holes and the smallest diameter thereat is0.35 μm. Therefore, considering that the diameter of the bottom surfaceof the hole which is nearer to the surface of the film to be processedis greater than 0.35 μm and that the film to be processed can besomewhat side-etched at the border region at the time of etching, a holeof a diameter much larger than the desired diameter is formed in thefilm to be processed. This tendency becomes marked particularly when thediameter of the resist pattern before baking is greater than 0.5 μm.

SUMMARY OF THE INVENTION

[0009] In view of the aforementioned, an object of the present inventionis to provide a method of forming a resist pattern in which a relativelylarge pattern, whose feature dimension is greater than the resolutionlimit of the KrF exposure technique, and an extremely fine pattern,whose feature dimension is less than or equal to the resolution limit ofthe KrF exposure technique, can be formed well simultaneously.

[0010] In order to achieve the above object, an aspect of the presentinvention is a method for forming a resist pattern including the stepsof: subjecting a resist, which is applied on a surface of an object tobe processed, to pattern exposure in which a first exposure amount forforming a pattern is applied to the resist; forming a resist pattern bydeveloping the resist; subjecting the resist pattern to a secondexposure in which a second exposure amount, which adjusts a shrinkagerate of the resist pattern, is applied to the resist pattern; andsubjecting the resist to a bake process at a temperature at which theresist flows.

[0011] Namely, for a resist pattern formed on an object to be processed,the heat resistance of the resist is changed by carrying out an exposurewhich applies a second exposure amount. The heat resistance of theresist affects the shrinkage rate of the resist pattern at the time ofhigh temperature bake processing. The greater the heat resistance, thelower the shrinkage rate. Because the heat resistance of the resistvaries in accordance with the second exposure amount, in the firstaspect of the present invention, the shrinkage rate of the resistpattern at the time of high temperature bake processing is adjusted byadjusting the second exposure amount.

[0012] Namely, a heat resistance of the resist is desired which is suchthat the shrinkage rate of the resist pattern is a predeterminedshrinkage rate. By applying the amount of exposure, which results inthis heat resistance, as the second exposure amount, the shrinkage rateof the resist pattern is adjusted, and the resist pattern can be shrunkto a desired dimension.

[0013] Control may be carried out such that second exposure amount isapplied to the resist pattern at the regions to be shrunk and theshrinkage rate of the resist pattern is adjusted such that the resistpattern is shrunk to a desired dimension. Conversely, control may becarried out such that the second exposure amount is applied to theresist pattern at the regions to be shrunk such that shrinkage of theresist pattern is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIGS. 1A-1E illustrate a flow of processing of a method offorming a resist pattern of a first embodiment of the present invention.

[0015]FIG. 2 is a diagram for explaining the schematic structure of astepper used in the first embodiment.

[0016]FIG. 3 is a graph illustrating the relationship between a secondexposure amounts and contact hole pattern shapes after high temperaturebake processing at 135° C. for 60 seconds.

[0017]FIG. 4 is a graph illustrating the relationship between bakingtemperatures and a contact hole pattern diameters.

[0018]FIG. 5 is a diagram illustrating a contact hole pattern dimensiondistribution which arises at the time of high temperature bakeprocessing in a square region which is 40 mm by 40 mm and is centeredaround an origin (0.0) which is a center of a wafer.

[0019]FIG. 6A is a diagram showing a distribution of contact holepattern dimensions at a wafer surface at the time of high temperaturebake processing at 135° C. for 60 seconds.

[0020]FIG. 6B is a diagram showing a distribution of correction exposureamounts at a wafer surface, as determined on the basis of FIG. 6A.

[0021]FIG. 6C is a diagram showing a distribution of contact holepattern dimensions at a wafer surface after the correction exposureamounts in FIG. 6B have been applied and then high temperature bakeprocessing has been carried out.

[0022]FIG. 7 is a diagram for explanation, and illustrates a schematicstructure of a batch exposure device used in a fourth embodiment.

[0023]FIG. 8A is a diagram showing a distribution of contact holepattern dimensions at a wafer surface at the time of high temperaturebake processing at 135° C. for 60 seconds.

[0024]FIG. 8B is a diagram showing a distribution of transmission ratesof a filter determined in accordance with correction exposure amountsbased on FIG. 8A.

[0025]FIG. 8C is a diagram showing a distribution of contact holepattern dimensions at a wafer surface after correction exposure amountsadjusted by the filter having the distribution of transmission rates ofFIG. 8B have been applied and then high temperature bake processing hasbeen carried out.

[0026]FIG. 9A is a diagram showing a distribution of the dispersion inthe shrinkage rate of a resist pattern caused by differences intemperature at a bake plate.

[0027]FIG. 9B is a diagram showing a distribution of the dispersion inthe pattern dimension at a wafer surface after etching using the resistpattern of FIG. 9A has been carried out.

[0028]FIG. 9C is a diagram showing a correction exposure amountdistribution which has been adjusted such that the dispersion in thedimension at the wafer surface after etching is eliminated.

[0029]FIG. 9D is a diagram showing a distribution of the dispersion inthe shrinkage rate of a resist pattern obtained by the correctionexposure amounts of FIG. 9C being applied and then high temperature bakeprocessing being carried out.

[0030]FIG. 9E is a diagram showing a distribution of the dispersion inthe pattern dimension arising at a wafer surface after etching by usingthe resist pattern of FIG. 9D has been carried out.

[0031]FIG. 10A is a diagram illustrating the configuration of a resistbefore high temperature bake processing, and is for explaining thedeterioration in the configuration of a resist pattern in a case inwhich a contact hole pattern, which is of a dimension which is less thanor equal to an exposure resolution, and a contact hole pattern, which isof a dimension which is greater than the exposure resolution, are formedsimultaneously by a conventional method of forming a resist pattern.

[0032]FIG. 10B is a diagram illustrating the configuration of a resistafter high temperature bake processing at 135° C. for 60 seconds, and isfor explaining the deterioration in the configuration of a resistpattern in a case in which a contact hole pattern, which is of adimension which is less than or equal to a dimension limited by anexposure resolution, and a contact hole pattern, which is of a dimensionwhich is greater than the dimension limited by the exposure resolution,are formed simultaneously by a conventional method of forming a resistpattern.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Embodiments of the present invention will be describedhereinafter with reference to FIGS. 1A through 4. In the embodiments,the method of forming a resist pattern and the exposure device of thepresent invention are applied to a case in which a KrF excimer laser isused as the light source, and a contact hole pattern of a resist isformed by using as the resist TDUR-P015 (manufactured by Tokyo OhkaKogyo Co., Ltd.), which is a type of resist used with UV light and is achemically-amplified positive resist used with KrF lasers.

First Embodiment

[0034] First, as illustrated in FIG. 1A, a silicon dioxide film (SiO₂film) 12, which is a film to be processed and is the object of etching,is formed on the surface of a wafer (substrate). TDUR-P015 is coatedonto the surface of the SiO₂ film 12 to a film thickness of, forexample, about 1.0 μm, to form a resist film 10.

[0035] Next, by using a stepper 30 structured as illustrated in FIG. 2(a stepping projection aligner; see FIG. 2; details to be describedlater), pattern exposure is carried out as shown in FIG. 1B per exposureunit region by using deep UV light of a wavelength of, for example, 248nm. At this time, a pattern is exposed on the resist film 10 at theregions to be shrunk, which pattern is of a dimension which is larger,in accordance with the shrinkage rate, than the dimension of the patternwhich is finally necessary. For example, a circular pattern of around0.25 μm is exposed at the regions to be shrunk. Further, a pattern whichis of a dimension which is finally required, e.g., a circular pattern ofabout 0.35 μm, is exposed at the regions not to be shrunk.

[0036] The amount of exposure applied to the resist film 10 at this timeis, for example, about 20 mJ/cm². This exposure amount is an exposureamount which is sufficient to form a pattern at the resist film 10 afterdevelopment (i.e., is the first exposure amount). Note that in FIG. 1B,for explanation, a first reticle 36 is disposed above the wafer.However, in actuality, the first reticle 36 is disposed between aprojection optical system 34 and a demagnification optical system 38 asshown in FIG. 2 which will be described later.

[0037] The stepper 30 used in exposure will now be briefly explainedwith reference to FIG. 2. The stepper 30 is basically formed by a KrFexcimer laser light source 32, the projection optical system 34, thefirst reticle 36, the demagnification optical system 38, an X-Y stage40, and a control section 42.

[0038] The KrF excimer laser light source 32 illuminates deep UV lightof a wavelength of, for example, 248 nm at a uniform intensity. Theprojection optical system 34 guides the UV light from the KrF excimerlaser light source 32 such that the UV light is illuminated onto thefirst reticle 36. In FIG. 2, the projection optical system 34 isillustrated as one lens, but is not limited to one lens and may beformed by plural lenses.

[0039] A circuit pattern is formed at the first reticle 36. In thepresent embodiment, the contact hole pattern of the regions to be shrunkis formed as a contact hole pattern of a dimension which is greater, inaccordance with the shrinkage rate, than the dimension which is finallyrequired. The pattern at the regions not to be shrunk is formed as acontact hole pattern of the dimension which is finally required. Thefirst reticle 36 can be changed, and in the present embodiment, a secondreticle 37 for a second exposure is used at the time of a secondexposure as will be described later.

[0040] The demagnification optical system 38 demagnifies the beam sizeof the UV light, which has passed through the first reticle 36, suchthat the beam size of the UV light is equal to a dimension of theexposure unit region, and illuminates the UV light onto a wafer disposedon the X-Y stage 40. The X-Y stage 40 is movable in two directions, theX direction and the Y direction which are orthogonal to one another, andis moved on the basis of instructions from the control section 42. Whenthere is an instruction from the control section 42 that exposure hasbeen completed for the exposure unit region which is currently beingexposed, the X-Y stage 40 is moved, by a unit which is the length of theexposure unit region, such that UV light from the KrF excimer laserlight source 32 is illuminated onto the next exposure unit region. Thecontrol section 42 effects on-off control of the KrF excimer laser lightsource 32 so as to adjust the illumination time of the UV light, andcontrols the movement of the X-Y stage 40 on the basis of positioninformation from a position detecting sensor (not shown in thedrawings).

[0041] When pattern exposure has been completed for all of the exposureunit regions of the wafer 14 by the stepper 30 structured as describedabove, the wafer 14 is removed from the stepper 30, and the resist isdeveloped by an alkaline aqueous solution. In this way, the exposedregions of the resist are removed, and as illustrated in FIG. 1C, at theregions to be shrunk, a contact hole pattern 22 a is formed which is ofa dimension which is larger, in accordance with the shrinkage rate, thanthe pattern dimension finally necessary (e.g., the contact hole pattern22 a of a diameter of about 0.25 μm is formed), and at the regions notto be shrunk, a contact hole pattern 20 of a dimension which is finallyrequired (e.g., a diameter of about 0.35 μm) is formed.

[0042] Next, the developed wafer 14 is again set on the stepper 30. Inplace of the first reticle 36, the second reticle 37 is set at which apattern is formed such that UV light is illuminated only onto theregions no to be shrunk. Then, as illustrated in FIG. 1D, exposure iscarried out by UV light. Here, the exposure amount of the UV light atthis time, i.e., the second exposure amount, is an amount (such as, forexample, 3.3 mJ/cm² or more) which leads to an improvement in the heatresistance of the TDUR-P015 forming the resist film 10 and which doesnot result in shrinking of the resist pattern after the subsequent hightemperature bake processing.

[0043] After exposure has been completed, the wafer 14 is removed fromthe stepper 30 (see FIG. 2), and is subjected to high temperature bakeprocessing at 135° C. for 60 seconds. Due to this high temperature bakeprocessing, for example, as illustrated in FIG. 11E, the contact holepattern 22 a, which has a diameter of about 0.25 μm and which is formedin the regions to be shrunk to which the second exposure amount is notapplied, is shrunk, so as to become a contact hole pattern 22 b of adiameter of about 0.1 μm. The pattern formed at the regions no to beshrunk, at which the second exposure amount is applied, remains as it isas the contact hole pattern 20 of a diameter of 0.35 μm, withoutshrinking. The second exposure amount, which provides sufficient heatresistance with respect to temperatures at the time of high temperaturebake processing at 135° C. for 60 seconds, is applied to the resistpattern at the regions which are not to be shrunk. Thus, a pattern ofdimensions which are substantially the same as those at the time thepattern was exposed, can be obtained.

[0044] Namely, if the TDUR-P015 is used as the resist in the secondexposure, as in the first exposure, a contact hole pattern has adifferent diameter after the high temperature bake processing at 135° C.for 60 seconds at the second exposure amount, as shown by the pointsrepresented by the diamonds in the graph of FIG. 3. In other words, whenthe second exposure amount is greater than or equal to about 3.3 mJ/cm²,the resist pattern has sufficient heat-resistance with respect totemperatures at the time of high temperature bake processing at 135° C.for 60 seconds. Thus, the diameter of the circular pattern, such as thecontact hole pattern, is substantially the same as the diameter (thevalue represented by the triangle in FIG. 3) of a circular pattern whichhas been obtained by an ordinary process in which regular bakeprocessing is carried out at 90° C. for 60 seconds and the secondexposure is not carried out.

[0045] On the other hand, when the second exposure amount is less thanaround 3.3 mJ/cm², the exposure is insufficient. Thus, the heatresistance with respect to temperatures at the time of high temperaturebake processing is insufficient. In other words, when the secondexposure amount is from 0 mJ/cm² to about 2.7 mJ/cm², the diameter ofthe circular pattern is substantially the same as the diameter (thevalue denoted by the square in FIG. 3) of a circular pattern obtained bya process in which high temperature bake processing is carried out at135° C. for 60 seconds without applying the second exposure amount.Further, when the second exposure amount is between about 2.7 mJ/cm² and3.3 mJ/cm², the heat resistance increases substantially proportionallyto the second exposure amount. Thus, the shrinkage rate decreasessubstantially proportionally, and the diameter of the circular patternwhich is finally obtained increases proportionally to the magnitude ofthe second exposure amount which is applied.

[0046] It suffices for the second exposure amount to be applied to arelatively large region. There is no need for the second exposure amountto be applied by using a high resolution exposure device such as thestepper 30 used at the time of pattern exposure. As a result, the secondexposure can be carried out by a relatively lower resolution exposuredevice which is other than the stepper 30 which carries out the patternexposure.

[0047] Namely, an exposure device equipped with a KrF excimer laser is arelatively new exposure device, and the number of such devices which areavailable is limited due to the cost thereof and the like. Accordingly,such devices have the highest frequency of usage. Thus, by using theexposure device equipped with a KrF excimer laser for pattern exposureand by applying the second exposure amount by using an exposure deviceof a different type which is not used frequently, the load on theexposure device having the high frequency of usage can be decreased, andefficient processing can be realized.

[0048] The light source of the exposure device used at this time may beany light source which illuminates light to which the resist isphotosensitive, and may be different than the light source for patternexposure. For example, the aforementioned TDUR-P015 is photosensitiveeven to i-line beams, and thus, the second exposure amount may beapplied by an exposure device which illuminates i-line beams. Further,the light source does not have to be a light source of a singlewavelength used in pattern exposure, and may be a light source whichilluminates light in a wide wavelength band including the singlewavelength region used for pattern exposure.

[0049] In the present embodiment, a case is explained in which TDUR-P015is used as the material forming the resist film 10. However, the resistfilm 10 is not limited to TDUR-P015, and other types of resists may beused provided that the resist has the property that the heat resistancethereof improves due to the application of the second exposure amount.Examples of such other resists include TDUR-P007 (manufactured by TokyoOhka Kogyo Co., Ltd.), TDUR-P422 (manufactured by Tokyo Ohka Kogyo Co.,Ltd.), SEPR402R (manufactured by Shin-Etsu Chemical Co., Ltd.), DX3200P(manufactured by Clariant Japan K.K.), and the like.

[0050] The shrinkage rate of the pattern corresponding to the secondexposure amount differs in accordance with the type of resist that isused. In this case, the second exposure amount should be adjusted tobecome the optimal UV light exposure amount on the basis ofrelationships between respective UV light exposure amounts and shrinkagerates.

[0051] In this way, in the present first embodiment, contact holepatterns of different diameters can be formed simultaneously without thepatterns deteriorating. For example, a contact hole pattern of adimension smaller than the resolution limit (such as a contact holepattern of a diameter of about 0.2 μm to a diameter of about 0.05 μm)and a contact hole pattern of a dimension which is larger than theresolution limit and which can be sufficiently formed by a conventionalexposure technique (such as a contact hole pattern of a diameter ofabout 0.2 μm or more) can be formed simultaneously.

Second Embodiment

[0052] As described above in the explanation of FIG. 3, the heatresistance of the TDUR-P015 used as the resist in the first embodimentincreases substantially proportionally when the second exposure amountis between about 2.7 mJ/cm² and 3.3 mJ/cm². Thus, the shrinkage ratedecreases substantially proportionally to the second exposure amount,and the diameter of the circular pattern which is finally obtainedincreases in proportion to the magnitude of the second exposure amount.

[0053] In the present second embodiment, in the above-described firstembodiment, after the second exposure amount is applied, a thirdexposure amount is applied to the entire surface of the wafer substrate.The third exposure amount is greater than or equal to the UV lightexposure amount at which the heat resistance begins to change, and isless than or equal to the UV light exposure amount at which the heatresistance is saturated (can be improved no more). The third exposureamount is, for example, from about 2.7 mJ/cm² to about 3.3 mJ/cm².

[0054] By applying the third exposure amount to the resist at theregions to be shrunk to which the second exposure amount is not applied,the shrinkage rate during the high temperature bake processing can befinely adjusted. Namely, by controlling the third exposure amount withinthe range of about 2.7 mJ/cm² to about 3.3 mJ/cm², the heat resistance,with respect to high temperature bake processing temperatures, of theresist at the regions to be shrunk changes. Thus, the shrinkage rate ofthe contact hole pattern at the regions to be shrunk after hightemperature bake processing can be finely adjusted.

[0055] The second exposure amount is applied to the regions no to beshrunk such that the pattern at the regions no to be shrunk is notshrunk during high temperature bake processing. Thus, even if the thirdexposure amount is applied to the regions no to be shrunk, the patterndoes not shrink, just as it does not shrink during the high temperaturebake processing. Accordingly, when applying the third exposure amount,there is no need to use a reticle, at which a pattern is formed, inorder to cover the regions no to be shrunk.

[0056] As illustrated in FIG. 3, for example, the relationship betweenthe UV light exposure amount and the dimensions to be finally obtainedor the shrinkage rate of the pattern is investigated in advance, and thethird exposure amount is determined on the basis of the obtainedrelationship such that the pattern dimension which is ultimatelyrequired can be obtained.

[0057] Here, for example, after a third exposure amount of 2.8 mJ/cm² isapplied to the resist pattern, high temperature bake processing at 135°C. for 60 seconds is carried out. Due to this high temperature bakeprocessing, the pattern formed at the regions not to be shrunk does notshrink, and the contact hole pattern 20 of the diameter of about 0.35 μmremains as it is. However, the amount of shrinkage of the contact holepattern of the diameter of about 0.25 μm formed at the regions to beshrunk is slightly less than in the previously-described firstembodiment, such that, for example, a contact hole pattern of a diameterof about 0.15 μm is obtained. Note that other processes are the same asthose of the first embodiment, and description thereof will therefore beomitted.

[0058] In this way, in accordance with the present second embodiment,contact hole patterns of different diameters can be formed wellsimultaneously without deterioration of the patterns, and also, can bereliably formed at the desired dimensions. In particular, a smallcontact hole pattern of a dimension which is less than or equal to theresolution limit and a contact hole pattern of a large dimension whichis greater than the resolution limit can be formed.

Third Embodiment

[0059] During the high temperature bake processing, local non-uniformityof temperature may arise at the bake plate such that temperaturedifferences of ±0.5° C. may arise at portions of the surface of thewafer which is disposed on the bake plate. As illustrated in FIG. 4, theshrinkage rate of the resist pattern at the time of high temperaturebake processing greatly varies in a vicinity of 130° C. even if thebaking temperature varies only by 1° C. Thus, in the high temperaturebake processing at 135° C., even in the same pattern, the shrinkage ratemay greatly differ depending on the position of the wafer surface. As aresult, as shown in FIG. 5, the diameter of the finally obtained contacthole pattern may vary from position to position of the wafer surface.

[0060] As a result, in the present third embodiment, a temperaturedifference distribution arising at the wafer surface at the time of hightemperature bake processing, such as the distribution shown in FIG. 5,is determined in advance. As shown in FIG. 4, the exposure amountsapplied to the respective unit regions are corrected so as to offset theerrors in the shrinkage rate which arise on the basis of the temperaturedifference distribution.

[0061] Namely, as illustrated in FIG. 6A, at the surface of a wafer forwhich high temperature bake processing at 135° C. for 60 seconds hasbeen completed, there are portions which have shrunk by more than theintended amount of shrinkage, such that regions (the portions indicatedby non-dense hatching, the portions indicated by dense hatching, and theblack portions) which are smaller than the designed dimensions areformed at portions of the wafer surface. In FIG. 6A, the shrinkage ratesamong these three types of portions increase in order with thenon-densely hatched portions having the lowest shrinkage rate, thedensely hatched portions having a higher shrinkage rate, and the blackportions having the highest shrinkage rate. The diameter of the formedcontact hole pattern becomes smaller in order from the non-denselyhatched portions to the densely hatched portions to the black portions.

[0062] Accordingly, before high temperature bake processing, asillustrated in FIG. 6B, exposure for correction is carried out. Theexposure at this time is carried out per unit exposure region. Incorrespondence with FIG. 6A, the correction exposure amount becomesgreater in order from the non-densely hatched portions to the denselyhatched portions to the black portions. The correction amounts at thistime are determined on the basis of the amount of change in theshrinkage rate and on the basis of the error temperature with respect tothe high temperature baking temperature of the region. Note that thereis no need for correction at the regions represented by the whiteportions, and thus, exposure processing for correction is not carriedout at these regions.

[0063] In this way, after high temperature bake processing has beencompleted, as illustrated in FIG. 6C, at a single wafer surface, thedimension shrinkage rates become substantially uniform. At a singlewafer surface, plural patterns which are substantially in accordancewith standard dimensions are obtained. Note that this exposure forcorrection may be carried out before the pattern exposure or after thecontact hole pattern has been formed.

[0064] In addition to variations in the high temperature bake processingtemperature, variations in the film thicknesses of the respective filmsforming the laminated layers on the wafer, and the like are causes forvariations occurring at the wafer surface. If the relationships betweenthe shrinkage rates and the positions of the wafer, which relationshipsare based on the variations in the film thicknesses of the respectivefilms (or based on other variations), are determined in advance, theshrinkage rates of the dimensions at a single wafer surface can be madeto be substantially uniform in the same way as described above.

[0065] In this way, in the present third embodiment, the exposure amountis corrected in accordance with any of various types of variations whichoccur at the wafer surface. Thus, the shrinkage rate of a pattern of awafer surface after high temperature bake processing can be made to besubstantially uniform, and the uniformity of the dimensions of thepattern can be improved.

Fourth Embodiment

[0066] The present fourth embodiment is an application of the thirdembodiment. The above-described correction is carried out at a batchexposure device structured as shown in FIG. 7. This batch exposuredevice is structured mainly by the KrF excimer laser light source 32,the projection optical system 34, a filter 44, and a stage 48.

[0067] The KrF excimer laser light source 32 illuminates deep UV lightof a wavelength of 248 nm at a uniform intensity. The projection opticalsystem 34 guides the UV light from the KrF excimer laser light source 32such that the light is irradiated onto the filter 44. Note that in FIG.7, although the projection optical system 34 is illustrated as one lens,the projection optical system 34 is not limited to one lens and may beformed by plural lenses.

[0068] The filter 44 adjusts the transmission rate per unit region whichis smaller than the unit regions forming one chip. Namely, asillustrated in FIG. 8A, at the surface of a wafer for which hightemperature bake processing at 135° C. for 60 seconds has beencompleted, there are portions which have shrunk by more than theintended amount of shrinkage, and regions (the portions indicated bynon-dense hatching, the portions indicated by dense hatching, and theblack portions in FIG. 8A) which are smaller than the standarddimensions are formed at portions of the wafer surface. In FIG. 8A, theshrinkage rates among these three types of portions increase in orderwith the non-densely hatched portions having the lowest shrinkage rate,the densely hatched portions having a higher shrinkage rate, and theblack portions having the highest shrinkage rate.

[0069] Accordingly, as illustrated in FIG. 8B, the transmission rate ofthe filter 44 becomes greater in order from the non-densely hatchedportions to the densely hatched portions to the black portions. Notethat there is no need for correction at the regions represented by thewhite portions, and thus, light is blocked from reaching these regions.

[0070] Exposure for correction is carried out in this way by the filter44 which adjusts the transmission rate. Thereafter, by carrying out hightemperature bake processing at 135° C. for 60 seconds, as illustrated inFIG. 8C, the amounts of shrinkage of the dimensions become substantiallyuniform at one wafer surface. At a single wafer surface, plural patternswhich are substantially in accordance with standard dimensions areobtained. Note that this exposure for correction may be carried outbefore the pattern exposure or after the contact hole pattern has beenformed.

[0071] In the batch exposure device of the present fourth embodiment,the KrF excimer laser light source 32 is used for the light source.However, the light source is not limited to the KrF excimer laser lightsource 32. A light source which is different than that used duringpattern exposure may be used, provided that it is a light source whichilluminates light to which the resist is photosensitive. In the same wayas in the above-described first embodiment, a light source which emitsi-line beams, a light source which emits light of a broad wavelengthband including the single wavelength region used for pattern exposure,or the like may be used.

[0072] By using the batch exposure device structured in this manner,throughput can be greatly improved. Because the structure of the batchexposure device is relatively simple, there is also the advantage thatmanufacturing of the batch exposure device is inexpensive.

Fifth Embodiment

[0073] As illustrated in FIG. 9B, there are cases in which the patterndimensions of the finally formed SiO₂ film 12 (see FIG. 1) greatly varydepending on the position on the surface of a single wafer. Thus,variations are caused by a factor in other processings such as etchingprocessing for etching the underlayer SiO₂ film 12 (see FIG. 1) by usingthe formed resist pattern as a mask.

[0074] Accordingly, in the present fifth embodiment, the exposureamounts applied to the respective unit regions are corrected such thatvariations in the dimensions at the surface of the one wafer to befinally obtained are eliminated.

[0075] For example, when a wafer has been subjected to high temperaturebake processing without being subjected to exposure for correctingvariations in the shrinkage rates caused by temperature differences ofthe bake plate, regions (the portions indicated by non-dense hatching,the portions indicated by dense hatching, and the black portions) whichare smaller than standard dimensions are formed at portions of the wafersurface as illustrated in FIG. 9A. Thereafter, when the underlayer SiO₂film 12 is etched by using the formed resist pattern as a mask,variations in dimensions such as shown in FIG. 9B arise among thedimensions of the finally obtained SiO₂ pattern.

[0076] In this case, a distribution of variations in the shrinkage rateof the wafer surface is determined (see FIG. 9D) such that the shrinkagedistribution after high temperature bake processing offsets thedistribution of variations in the final dimensions shown in FIG. 9B.Exposure amounts (FIG. 9C) for correcting the variations in shrinkagerates are determined such that the distribution in variations in theshrinkage rate, which are caused by the differences in the temperatureof the bake plate as shown in FIG. 9A, becomes the distribution ofvariations in the shrinkage rates shown in FIG. 9D.

[0077] By adjusting the exposure amounts (FIG. 9C) for correcting thevariations in the shrinkage rates in this manner, as shown in FIG. 9E,the shrinkage rates of the dimensions become substantially uniform at asurface of a single wafer for which processing has been completed. At asingle wafer surface, plural patterns which are substantially inaccordance with standard dimensions are obtained. Note that thisexposure for correction may be carried out by the stepper 30 describedin the first embodiment, or by the batch exposure device described inthe fourth embodiment.

[0078] The first through the fifth embodiments have described cases inwhich the patterns which are formed are all contact hole patterns.However, the present invention is of course applicable to other types ofpatterns, such as resist patterns at the time of forming an embeddedwiring pattern or the like.

[0079] In the first through the fifth embodiments, the high temperaturebake processing temperature is 135° C. However, the high temperaturebake processing temperature is not particularly limited to thistemperature, and may be appropriately varied in accordance with the typeof the resist or the like. Further, the shrinkage rates of the resistpattern can be adjusted not only by adjusting at least one of the secondexposure amount and the third exposure amount, but also by adjusting thehigh temperature bake processing temperature. Thus, the high temperaturebake processing temperature can be varied in order to control theshrinkage rates of the resist pattern. The shrinkage rates can beadjusted even more precisely by controlling both the adjustment of atleast one of the second exposure amount and the third exposure amount,and the adjustment of the high temperature bake processing temperature.

[0080] In the first through the fifth embodiments, cases are describedin which exposure is carried out by using a KrF excimer laser lightsource. However, if the resist, which is selected in accordance with thetype of exposure light to be used, has the property that the heatresistance thereof with respect to the baking temperature can be variedin accordance with the exposure amount, exposure can be carried out by,for example, using an ArF excimer laser light source.

[0081] The sizes of the contact hole patterns in the first through fifthembodiments are all examples, and the present invention is not limitedto these sizes. The size of the contact hole pattern can be selectedappropriately in accordance with the object. Further, the shrinkagerates of the contact hole patterns are also examples, and are of coursevalues which vary in accordance with the type of the resist that isused.

[0082] As described above, the present invention has following effects.

[0083] Both a pattern of a relatively large dimension which is greaterthan or equal to the resolution limit, and a pattern of a relativelyfine dimension which is less than or equal to the resolution limit, canbe formed simultaneously. Further, a resist pattern which is formed wellwithout deterioration of the configuration thereof can be obtained.

[0084] The shrinkage rates at the surface of one wafer can be made to besubstantially the same, even when there are differences in temperatureat the surface of one wafer caused by the heating state or the like of aheating body such as a bake plate at the time of high temperature bakeprocessing.

[0085] The shrinkage rates at the surface of one wafer can be made to besubstantially the same by correcting variations in dimensions whichoccur at the surface of the one wafer due to processes other than thehigh temperature bake processing.

[0086] The shrinkage rate of the pattern at the time of high temperaturebaking can be adjusted even more precisely.

[0087] The exposure device has a relatively simple structure, and thecosts for manufacturing the exposure device are low. In addition, theexposure device can carry out the second exposure, the third exposure,and the exposure for correction. Thus, the load on an exposure device,which has a KrF excimer laser as the light source and which has a highfrequency of usage, can be decreased.

What is claimed is:
 1. A method of forming a resist pattern comprisingthe steps of: subjecting a resist, which is applied on a surface of anobject to be processed, to pattern exposure in which a first exposureamount for forming a pattern is applied to the resist; forming a resistpattern by developing the resist; subjecting the resist pattern to asecond exposure in which a second exposure amount, which adjusts ashrinkage rate of the resist pattern, is applied to the resist pattern;and subjecting the resist to a bake process at a temperature at whichthe resist flows.
 2. The method of forming a resist pattern of claim 1,wherein the second exposure amount is an exposure amount which is atleast equal to a saturation exposure amount of the resist.
 3. The methodof forming a resist pattern of claim 1, wherein the resist patternincludes regions to be shrunk at a predetermined shrinkage rate andregions not to be shrunk, and the step of subjecting the resist patternto a second exposure includes the sub-step of exposing regions to beshrunk at the second exposure amount, which corresponds to thepredetermined shrinkage rate, and exposing regions not to be shrunk at athird exposure amount which provides the resist pattern with resistanceto shrinkage during the step of subjecting the resist to a bake process.4. The method of forming a resist pattern of claim 1, further comprisingthe step of: adjusting the second exposure amount for each ofpredetermined regions of the object to be processed in accordance withshrinkage rate differentials due to a distribution of temperaturesarising during the step of subjecting the resist to a bake process. 5.The method of forming a resist pattern of claim 1, further comprisingthe step of: correcting the second exposure amount for each ofpredetermined regions of the object to be processed for eliminating adistribution of errors in shrinkage rates of a pattern to finally beformed on the object.
 6. The method of forming a resist pattern of claim4, wherein the step of adjusting the second exposure amount is carriedout at the time of second exposure by adding a correction amount to apre-correction second exposure amount.
 7. The method of forming a resistpattern of claim 4, wherein the step of adjusting the second exposureamount is carried out by performing an additional exposure at anexposure amount corresponding to a correction amount, after the secondexposure has been carried out at a pre-correction second exposureamount.
 8. The method of forming a resist pattern of claim 5, whereinthe step of adjusting the second exposure amount is carried out at thetime of second exposure by adding a correction amount to apre-correction second exposure amount.
 9. The method of forming a resistpattern of claim 5, wherein the step of adjusting the second exposureamount is carried out by performing an additional exposure at anexposure amount corresponding to a correction amount, after the secondexposure has been carried out at a pre-correction second exposureamount.
 10. The method of forming a resist pattern of claim 1, whereinthe resist is a resist for use with UV light, and exposures areperformed using UV light.
 11. The method of forming a resist pattern ofclaim 1, further comprising the step of: adjusting the shrinkage rate ofthe resist pattern by adjusting bake temperature while subjecting theresist to the bake process.
 12. A device for exposure of an objectsurface having a predetermined shrinkage rate during bake processing ofthe object following exposure, the device comprising: (a) an opticalsystem having a light source which when operated irradiates light of asubstantially uniform intensity towards a target location, whichlocation is for placement of the object surface thereat for exposure;(b) a filter provided between the target location and the light source,the filter having an adjustable transmission rate, which passes lightirradiated from the light source therethrough for each of predeterminedregions of the object surface in an exposure amount corresponding to apredetermined shrinkage rate for the object surface when bake processedfollowing exposure.
 13. The device of claim 12, wherein the transmissionrate of the filter is corrected for each predetermined region of theobject surface for reducing a distribution of errors in the shrinkagerate, which distribution corresponds to a temperature distributionarising in the object during the bake process.
 14. The exposure deviceof claim 12, wherein the transmission rate of the filter is correctedfor each predetermined region of the object to be processed for reducinga distribution of errors in the shrinkage rate for forming a finalpattern on the object surface.
 15. A method of forming a resist pattern,comprising the steps of: (a) applying a resist to an object surface; (b)subjecting the resist to pattern exposure by irradiating the resist withlight directed through a first reticle; (c) developing the resist; (d)adjusting a shrinkage rate of the resist pattern by irradiating theresist with light directed through a second reticle; and (e) baking theresist.
 16. The method of claim 15, wherein the step of adjusting ashrinkage rate includes irradiating areas of the resist with light of atleast 2.7 mJ/cm².
 17. The method of claim 15, wherein the step ofadjusting a shrinkage rate includes irradiating areas of the resist withlight of at least 3.3 mJ/cm².
 18. The method of claim 15, wherein thestep of adjusting a shrinkage rate includes providing the second reticlefor passing light therethrough for exposing areas of the resist whichare not to be shrunk.
 19. The method of claim 15, further comprising thestep of irradiating the resist with light in an amount from 2.7 to 3.3mJ/cm².
 20. The method of claim 19, wherein the step of irradiating theresist with light in the amount from 2.7 to 3.3 mJ/cm² includesirradiating areas of the resist in accordance with temperaturedifferentials that arise in the resist during the step of baking.